Improved methods of fabricating electronic and/or mechanical structures continue to drive the electronics and other industries. More and more components are being added to devices that are getting increasingly complex and smaller. As a result fabrication techniques are required to provide electronic and/or mechanical components and/or parts that have increased functionality as well as to take up less space in the device and on substrates used in the device. The fields of micro-mechatronics, microsensors such as multi-axis gyroscopes, electrical circuits, and microwave and waveguide circuits are rapidly advancing. The ability to achieve customization in such devices and still allow them to be affordably manufactured has remained a challenge. Most industrial shaping, forming, and production processes achieve economy of scale only by near direct duplication of a device. For example, consumer electronics are affordable when making millions of complex integrated circuits that are nearly identical. Still there are many fields where the ability to make custom 3D parts of heterogeneous materials has remained elusive and substantial sacrifices in dimensional accuracy and precision, material diversity, upward or downward size scaling, for example from microns to meters, and/or other limitations have relegated most direct 3D manufacturing to either be unaffordable, impractical, or find limited fields of use, for example to make plastic prototypes for novelty, engineering understanding, or marketing.
In micromechanics, processes to make small components often revolve around removal rather than additive processes such as turning or milling operations and such devices are typically made one at a time. Alternatively, molding is used but is limited in the complexity of the parts and number that can be made and are usually of limited material diversity. For example, one would not expect injection molding to make parts of plastic, metal, and ceramic in the same molding operation. Processes that have been created to address the fabrication of components and devices of very high precision and accuracy traditionally revolve around photolithographic processes and deposition and/or etching processes. For example, in traditional thin film metallization patterning for integrated circuits and circuit boards, temporary photoresists are patterned on metallic layers followed by etching of the exposed metal, then removed to leave a metallic pattern. Alternatively, metal can be plated into the exposed areas of the photoresist followed by removal of the photoresist and flash etching to leave behind a metallic pattern. Thicknesses of the patterns are limited to the thickness of the original metallic layer, in the case of etching, and the thickness of the photoresist, in the case of metallic plating.
Current fabrication processes include, for example, permanent resists, generally known as photoimageable dielectrics (PID). It may desirable that such materials have low dielectric constants and low dielectric losses particularly when they are a permanent part of an electronic component and/or device. They are coated onto a substrate from either a liquid composition or by using a dry film, indiscriminately, coating the entire substrate. They can be used to photodefine structures wherein the PID can be cured to become a permanent part of the electronic and/or mechanical component and/or device. Adhesion promotion and catalyzation of the surfaces of the cured PID may allow for metal to be deposited onto the surfaces of the resist.
In some processes, a temporary photoresist may be metallized or the resist may serve as a mold for the metallization; this is followed by removal of the resist leaving behind a metal structure with air as the dielectric. In addition, many structures require more than one layer of dielectric material and/or conductive materials such as, for example, metal. To create devices that have substantial complexity, tens, hundreds, or even millions of layers may be required depending on the size, scale, and resolution desired. Furthermore, the use of PIDs to create such devices is very limiting. After a layer of PID is imaged to form a structure, a second layer, uniformly applied from either a liquid or a dry film, has difficulty planarizing or filling the spaces in the structure particularly if they are on the scale of the layer's thickness or greater. A further limitation is the inability to create structures of varying and specific desired thicknesses since the PID can only be applied as one uniform thickness when applied by these methods. Still a further limitation is the inability of the PID to allow for selective metallization. Adhesion promotion and catalyzation of the PID surfaces is non-selective so that every exposed surface will be metallized, rather than a select set of surfaces.
A still further limitation of the current techniques is the inability to create structures that differ substantially in size, functionality, and accuracy and also can provide the needed material diversity wherein the materials have both acceptable properties in comparison to other forming techniques currently known—for example finding a process that can provide the properties of metals, dielectrics, and some polymer materials that can be achieved through means such as thin film deposition, plating, sintering, and so on. Even without material diversity, the materials available in the 3D printing processes themselves often have compromised material properties compared to the material available in bulk or through other forming methods. This is particularly true when attempting to create multicomponent structures in the 3D printing process. For example, the properties of a 3D printed conductor or metallization may have unacceptably low electrical or thermal conductivity compared to a vacuum deposited or plated counterpart. For a dielectric such as a ceramic, or even a polymer composition, properties such as the dielectric constants, dielectric losses, and density may be unacceptably compromised. Thus, it may prove unacceptably challenging to obtain a suitable diversity of desirable materials, having a large enough set of desirable material properties, to create many functional devices that would be desired, for example, that which would desirably be associated with creating a 3D printed and fully functional version of many components populating an electronic and/or mechanical device. For instance, to create a circuit board, both a good electrical conductor and a good non conductor are required in a pattern. It may also be important in the final device that its metals or conductors are able to take a solder based device attachment; and that its adjacent non-conductors can withstand the temperatures associated with this process. Finding a 3D printing process that can provide metal properties found in plated metals and in the same process finding a dielectric that will both suitably adhere to said printed metal and have an acceptable decomposition temperature, chemical resistance, and other suitable dielectric properties can be difficult with the processes currently available in 3D printing.
The current processes are of little use when a substrate has components or other elements already fabricated onto or into the substrate particularly where the topology is substantially non-planar with respect to the layer thickness. Also, many substrates are sensitive to the solvents or heating steps that are required in fabrication. Alternative methods of preparing these devices with many components include molds and pick and place processes wherein the components are made “off-line” and are assembled later onto the electronic and/or mechanical device. Classic examples include capacitors and resistors, and inductors as well as magnetic components.
As can be seen, current methods for the fabrication of electronic and mechanical structures for manufacturing electronic and/or mechanical components and other objects are limiting. Thus, there is a need for devices and methods of fabrication that allow electronic and/or mechanical structures to be made with varying sizes, thicknesses, and materials as well as the ability to be preferentially metallized—including devices and methods that can be utilized in a non-destructive manner when substrates are already populated with devices.